Process for controlled radical polymerization in aqueous dispersion

ABSTRACT

The present invention relates to a process for controlled radicalpolymerization in aqueous dispersion in the presence of selected nitroxyl radicals having a defined partition equilibrium between water and monomer as measured by their log p. wherein p is the partition coefficient of the nitroxyl radical in octanol and water.

The present invention relates to a process for controlled radicalpolymerization in aqueous dispersion in the presence of selectednitroxyl radicals having a defined partition equilibrium between waterand monomer as measured by their log p, wherein p is the partitioncoefficient of the nitroxyl radical in octanol and water.

Polymerization processes using water as a continuous dispersing phasewherein initially the monomers and after polymerization the polymers aredispersed are widely used for manufacturing polymers (aqueous dispersionpolymerization). Mostly, water and a water-insoluble monomer, anemulgator and/or a protective colloid and a suitable initiator systemare mixed by generally known methods building a monomer swollen micellarsystem or stabilized monomer droplets.

Of particular interest are emulsion polymerizations, wherein usuallywater soluble initiator systems are used.

The monomers are essentially insoluble in the aqueous phase and formfinely distributed droplets therein. The addition of dispersing agentssuch as for example sodium dodecyl-sulfate is in many cases necessary toachieve such stable droplets and micelles. Examples of dispersing agentsare for example given in “Ullmann Enzyklopädie der technischen Chemie,Bd.10, 4. Auflage, Verlag Chemie, Weinheim (1975), page 449”.

Several variations are known in the state of the art, for exampleemulgator free emulsion polymerization, mini emulsion polymerization andmicro emulsion polymerization. These variations are characterized bychanges of kind and amount of the emulgator and initiator systemsleading to different polymer products especially with regard tomolecular weight, polymer particle size and their distributions.

Polymers or copolymers prepared by free radical polymerization processesinherently have broad molecular weight distributions or polydispersitieswhich are generally higher than about four. One reason for this is thatmost of the free radical initiators have half lives that are relativelylong, ranging from several minutes to many hours, and thus the polymericchains are not all initiated at the same time and the initiators providegrowing chains of various lengths at any time during the polymerizationprocess. Another reason is that the propagating chains in a free radicalprocess can react with each other in processes known as combination anddisproportionation, both of which are irreversibly chain-terminatingreaction processes. In doing so, chains of varying lengths areterminated at different times during the reaction process, resulting inresins consisting of polymeric chains which vary widely in length fromvery small to very large and which thus have broad polydispersities. Ifa free radical polymerization process is to be used for producing narrowmolecular weight distributions, then all polymer chains must beinitiated at about the same time and termination of the growingpolymer-chains by combination or disproportionation processes must beavoided.

A method to reduce polydispersity and to avoid the disadvantages ofconventional radical polymerization has already been described bySolomon et al., U.S. Pat. No. 4,581,429, issued Apr. 8, 1986, wherein afree radical polymerization process is disclosed which controls thegrowth of polymer chains to produce short chain or oligomerichomopolymers and copolymers, including block and graft copolymers. Theprocess employs an initiator having the formula (in part) R′R″N—O—X,where X is a free radical species capable of polymerizing unsaturatedmonomers. The reactions typically have low conversion rates.Specifically mentioned radical R′R″N—O. groups are derived from 1,1,3,3tetraethylisoindoline, 1,1,3,3 tetrapropylisoindoline, 2,2,6,6tetramethylpiperidine, 2,2,5,5 tetramethylpyrrolidine ordi-t-butylamine.

In WO 99/00426 emulsion polymerization of ethylenically unsaturatedmonomers in the presence of nitroxyl radicals has been described ingreater detail, pointing out that the monomer droplets have a size ofless or equal 500 nm.

Recently in EP 970973 emulsion polymerization in the presence of astable free radical has been described, pointing out that the watersolubility of the stable free radical is at least 0.1 g/l at 25° C.Additionally, in WO 99/11674 the requirement of the molale solubility ofthe nitroxyl radicals in the aqueous medium is described as being atleast 10⁻⁶ mol/kg and most preferred at least 10⁻¹ mol/kg at 25° C. and1 bar.

In the instant invention it has been found, that the most importantproperty of the nitroxyl radicals is not the good solubility in waterbut the partition equilibrium between water and monomer as reflected bythe log p value of the nitroxyl. The right balance between solubility inwater and solubility in the monomer droplets influences strongly theefficiency in terms of polydispersity, rate of polymerization and yield.

The partition coefficient log p (octanol/water) is a widely usedparameter for example in rating the environmental impact of chemicalcompounds. Its calculation is described by W. M. Meylan, P. H. Howard inJ. Pharmaceutical Sciences 84, (1995), 83-92.

One subject of the instant invention is a process for preparing anoligomer, a cooligomer, a polymer or a copolymer (block or random) byfree radical polymerization in aqueous dispersion of at least oneethylenically unsaturated monomer or oligomer, which comprises formingan aqueous dispersion, having the monomer in the disperse phase and(co)polymerizing the monomer or monomers/oligomers at elevatedtemperature in the presence of

a) at least one stable free nitroxyl radical which has a log p(octanol/water) of between −0.5 and 7.5 and which is selected from thegroup consisting of a compound of formula (A), (B), (C), (D), (E), (F),(G), (H) or (I)

wherein

R is hydrogen, C₁-C₁₈alkyl which is uninterrupted or interrupted by oneor more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalentradical of an aliphatic carboxylic-acid having 2 to 18 carbon atoms, ofa cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or anα,β-unsaturated carboxylic acid having 3 to 5 carbon atoms or of anaromatic carboxylic acid having 7 to 15 carbon atoms;

R₁₀₁ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl,C₃-C₅alkenoyl or benzoyl;

R₁₀₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl, C₂-C₈alkenyl unsubstituted orsubstituted by a cyano, carbonyl or carbamide group, or is glycidyl, agroup of the formula —CH₂CH(OH)—Z or of the formula —CO—Z or —CONH—Zwherein Z is hydrogen, methyl or phenyl;

G₆ is hydrogen and G₅ is hydrogen or C₁-C₄alkyl, and

G₁ and G₃ are methyl and G₂ and G₄ are ethyl or propyl or G₁ and G₂ aremethyl and G₃ and G₄ are ethyl or propyl;

R₁, R₂, R₃ and R₄ independently of each other are C₁-C₁₈alkyl,C₃-C₁₈alkenyl, C₃-C₁₈alkinyl, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinylwhich are substituted by OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkylwhich is interrupted by at least one O atom and/or NR₅ group,C₃-C₁₂cycloalkyl or C₆-C₁₀aryl or R₁ and R₂ and/or R₃ and R₄ togetherwith the linking carbon atom form a C₃-C₁₂cycloalkyl radical;

R₅, R₆ and R₇ independently are hydrogen, C₁-C₁₈alkyl or C₆-C₁₀aryl;

R₈ is hydrogen, OH, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl;

C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl which are substituted by oneor more OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkyl which isinterrupted by at least one O atom and/or NR₅ group, C₃-C₁₂cycloalkyl orC₆-C₁₀aryl, C₇-C₉phenylalkyl, C₅-C₁₀heteroaryl, —C(O)—C₁-C₁₈alkyl,—O—C₁-C₁₈alkyl or —COOC₁-C₁₈alkyl; and

R₉, R₁₀, R₁₁ and R₁₂ are independently hydrogen, phenyl or C₁-C₁₈alkyl;and

b) a free radical initiator.

The alkyl radicals in the various substituents may be linear orbranched. Examples of alkyl containing 1 to 18 carbon atoms are methyl,ethyl, propyl, isopropyl, butyl, 2-butyl, isobutyl, t-butyl, pentyl,2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, t-octyl, nonyl, decyl,undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl and octadecyl.

Alkenyl with 3 to 18 carbon atoms is a linear or branched radical as forexample propenyl, 2-butenyl, 3-butenyl, isobutenyl, n-2,4pentadienyl,3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl, iso-dodecenyl, oleyl,n-2-octadecenyl oder n4-octadecenyl. Preferred is alkenyl with 3 bis 12,particularly preferred with 3 to 6 carbon atoms.

Alkinyl with 3 to 18 is a linear or branched radical as for examplepropinyl (—CH₂—C≡CH), 2-butinyl, 3butinyl, n-2-octinyl, odern-2-octadecinyl. Preferred is alkinyl with 3 to 12, particularlypreferred with 3 to 6 carbon atoms.

Examples for hydroxy substituted alkyl are hydroxy propyl, hydroxy butylor hydroxy hexyl.

Examples for halogen substituted alkyl are dichloropropyl,monobromobutyl or trichlorohexyl.

C₂-C₁₈alkyl interrupted by at least one O atom is for example—CH₂—CH₂—O—CH₂—CH₃, —CH₂—CH₂—O—CH₃— or —CH₂—CH₂—O—CH₂—CH₂—CH₂—O—CH₂—CH₃,—CH₂—. It is preferably derived from polyethlene glycol. A generaldescription is —((CH₂)_(a)—O)_(b)—H/CH₃, wherein a is a number from 1 to6 and b is a number from 2 to 10.

C₂-C₁₈alkyl interrupted by at least one NR₅ group may be generallydescribed as —((CH₂)_(a)—NR₅)_(b)—H/CH₃, wherein a, b and R₅ are asdefined above.

C₃-C₁₂cycloalkyl is typically, cyclopropyl, cyclopentyl,methylcyclopentyl, dimethylcyclopentyl, cyclohexyl, methylcyclohexyl ortrimethylcyclohexyl.

C₆-C₁₀ aryl is for example phenyl or naphthyl, but also comprised areC₁-C₄alkyl substituted phenyl, C₁-C₄alkoxy substituted phenyl, hydroxy,halogen or nitro substituted phenyl. Examples for alkyl substitutedphenyl are ethylbenzene, toluene, xylene and its isomers, mesitylene orisopropylbenzene. Halogen substituted phenyl is for exampledichlorobenzene or bromotoluene.

Alkoxy substituents are typically methoxy, ethoxy, propoxy or butoxy andtheir corresponding isomers.

C₇-C₉phenylalkyl is benzyl, phenylethyl or phenylpropyl.

C₅-C₁₀heteroaryl is for example pyrrol, pyrazol, imidazol,2,4,dimethylpyrrol, 1-methylpyrrol, thiophene, furane, furfural, indol,cumarone, oxazol, thiazol, isoxazol, isothiazol, triazol, pyridine,α-picoline, pyridazine, pyrazine or pyrimidine.

If R is a monovalent radical of a carboxylic acid, it is, for example,an acetyl, propionyl, butyryl, valeroyl, caproyl, stearoyl, lauroyl,acryloyl, methacryloyl, benzoyl, cinnamoyl orβ-(3,5-di-tert-butylhydroxyphenyl)propionyl radical.

C₁-C₁₈alkanoyl is for example, formyl, propionyl, butyryl, octanoyl,dodecanoyl but preferably acetyl and C₃-C₅alkenoyl is in particularacryloyl.

The above compounds and their preparation are described in GB 2335190and in GB 2342649.

Preferred is a process, wherein in formula A, B and C

R is hydrogen, C₁-C₁₈alkyl, cyanoethyl, benzoyl, glycidyl, a monovalentradical of an aliphatic, carboxylic acid;

R₁₀₁, is C₁-C₁₂alkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoyl orbenzoyl;

R₁₀₂ is C₁-C₁₈alkyl, glycidyl, a group of the formula —CH₂CH(OH)-Z or ofthe formula —CO-Z, wherein Z is hydrogen, methyl or phenyl.

Another preferred process is, wherein in formula (D), (E), (F), (G), (H)and (I) at least two of R₁, R₂, R₃ and R₄ are ethyl, propyl or butyl andthe remaining are methyl; or

R₁ and R₂ or R₃ and R₄ together with the linking carbon atom form aC₅-C₆cycloalkyl radical and one remaining substituents is ethyl, propylor butyl.

Specific particularly suitable compounds are given in the followingTable.

Compound No. Nitroxyl-Radical log p 101

2.6 102

3.0 103

2.2 104

7.4 105

5.9 106

4.9 107

4.0 108

3.5 109

2.4 110

5.1 111

4.6 112

1.5 113

6.8 114

4.9 115

5.6 116

4.6 117

2.0 118

6.8 119

5.8 120

4.9 121

3.9 122

1.9 123

3.6 124

3.1

Preferably log p is from 0 to 5 and more preferably from 1 to 5.

Preferably the free radical initiator of component b) is a bis-azocompound, a peroxide or a hydroperoxide.

Specific preferred radical sources are 2,2′-azobisisobutyronitrile,2,2′-azobis(2-methyl-butyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),1,1′-azobis(1-cyclohexanecarbonitrile), 2,2′-azobis(isobutyramide)dihydrate, 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile,dimethyl-2,2′-azobisisobutyrate, 2-(carbamoylazo)isobutyronitrile,2,2′-azobis(2,4,4-trimethylpentane), 2,2′-azobis(2-methylpropane),2,2′-azobis(N,N′-dimethyleneisobutyramidine), free base orhydrochloride, 2,2′-azobis(2-amidinopropane), free base orhydrochloride,2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide} or2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide;acetyl cyclohexane sulphonyl peroxide, diisopropyl peroxy dicarbonate,t-amyl pemeodecanoate, t-butyl pemeodecanoate, t-butyl perpivalate,t-amylperpivalate, bis(2,4-dichlorobenzoyl)peroxide, diisononanoylperoxide, didecanoyl peroxide, dioctanoyl peroxide, dilauroyl peroxide,bis (2-methylbenzoyl) peroxide, disuccinic acid peroxide, diacetylperoxide, dibenzoyl peroxide, t-butyl per 2-ethylhexanoate,bis-(4-chlorobenzoyl)-peroxide, t-butyl perisobutyrate, t-butylpermaleinate, 1,1-bis(t-butylperoxy)3,5,5-trimethylcyclohexane,1,1-bis(t-butylperoxy)cyclohexane, t-butyl peroxy isopropyl carbonate,t-butyl perisononaoate, 2,5-dimethylhexane 2,5dibenzoate, t-butylperacetate, t-amyl perbenzoate, t-butyl perbenzoate, 2,2-bis(t-butylperoxy) butane, 2,2 bis (t-butylperoxy) propane, dicumylperoxide, 2,5dimethylhexane-2,5-di-t-butylperoxide, 3-t-butylperoxy3-phenylphthalide, di-t-amyl peroxide, α,α′-bis(t-butylperoxy isopropyl)benzene, 3,5-bis (t-butylperoxy)3,5-dimethyl 1,2-dioxolane, di-t-butylperoxide, 2,5-dimethylhexyne-2,5-di-t-butylperoxide,3,3,6,6,9,9-hexamethyl 1,2,4,5-tetraoxa cyclononane, p-menthanehydroperoxide, pinane hydroperoxide, diisopropylbenzenemono-α-hydroperoxide, cumene hydroperoxide or t-butyl hydroperoxide.

The radical initiator has preferably a water solubility of at least 1g/l at 20° C.

Most preferred are the following compounds, which are all commerciallyavailable.

WAKO VA-061

WAKO V-501

WAKO V-30

WAKO VA-086

WAKO VA-044

WAKO V-50

Natrium-peroxodisulfat Kalium-peroxodisulfat Ammonium-peroxodisulfat

It is also possible to use combinations of Fe-compounds or Co-compoundswith peroxo salts or salts of bisulfites or hydrosulfites. Thesecombinations are known as redox systems.

Preferably the ethylenically unsaturated monomer is selected from thegroup consisting of styrene, substituted styrene, conjugated dienes,acrolein, vinyl acetate, vinylpyrrolidone, vinylimidazole, maleicanhydride, (alkyl)acrylic acidanhydrides, (alkyl)acrylic esters,(meth)acrylonitriles, (alkyl)acrylamides.

More preferred the ethylenically unsaturated monomer is an acrylic acidester, acrylamide, acryinitrile, methacrylic acid ester, methacrylamide,methacrylnitrile.

A preferred ethylenically unsaturated monomer conforms to formulaCH₂═C(R_(a))—(C═Z)—R_(b), wherein R_(a) is hydrogen or C₁-C₄alkyl, R_(b)is NH₂, glycidyl, unsubstituted C₁-C₁₈alkoxy, C₂-C₁₀₀alkoxy interruptedby at least one N and/or O atom, or hydroxy-substituted C₁-C₁₈alkoxy,unsubstituted C₁-C₁₈alkylamino, di(C₁-C₁₈alkyl)amino,hydroxy-substituted C₁-C₁₈alkylamino or hydroxy-substituteddi(C₁-C₁₈alkyl)amino or —O—CH₂—CH₂—N(CH₃)₂;

Z is oxygen or sulfur.

Examples for R_(b) as C₂-C₁₀₀alkoxy interrupted by at least one O atomare of formula

wherein R_(c) is C₁-C₂₅alkyl, phenyl or phenyl substituted byC₁-C₁₈alkyl, R_(d) is hydrogen or methyl and v is a number from 1 to 50.These monomers are for example derived from non ionic surfactants byacrylation of the corresponding alkoxylated alcohols or phenols. Therepeating units may be derived from ethylene oxide, propylene oxide ormixtures of both.

Further examples of suitable acrylate or methacrylate monomers are givenbelow.

Further acrylate monomers are

Examples for suitable monomers other than acrylates are

Preferably R_(a) is hydrogen or methyl, R_(b) is NH₂, gycidyl,unsubstituted or with hydroxy substituted C₁-C₄alkoxy, unsubstitutedC₁-C₄alkylamino, di(C₁-C₄alkyl)amino, hydroxy-substitutedC₁-C₄alkylamino or hydroxy-substituted di(C₁-C₄alkyl)amino; and

Z is oxygen.

Preferably the aqueous phase is from 25 to 95% more preferably from 40to 80% and most preferred from 45 to 75% by weight, based on the totalmixture.

The total mixture contains water, at least one monomer, the abovementioned regulator and initiator and in many cases at least onesurfactant and/or a organic solvent.

Optionally other water miscible solvents may be present usually lessthan 10% by weight based on the water content. Exemplary cosolventsuseful in the present invention may be selected from the groupconsisting of aliphatic alcohols, glycols, ethers, glycol ethers,pyrrolidines, N-alkyl pyrrolidinones, N-alkyl pyrrolidones, polyethyleneglycols, polypropylene glycols, amides, carboxylic acids and saltsthereof, esters, organosulfides, sulfoxides, sulfones, alcoholderivatives, hydroxyether derivatives such as butyl carbitol orcellosolve, amino alcohols, ketones, and the like, as well asderivatives thereof and mixtures thereof. Specific examples includemethanol, ethanol, propanol, dioxane, ethylene glycol, propylene glycol,diethylene glycol, glycerol, dipropylene glycol, tetrahydrofuran, andother water-soluble or water-miscible materials, and mixtures thereof.

Preferred are water, water alcohol mixtures, water ethylene glycol orpropylene glycol mixtures, water acetone, water tetrahydrofurane, orwater dimethylformamide mixtures.

Preferably the solids content of the resulting polymer dispersion isbetween 15-60% by weight.

Preferably the nitroxyl radical of component a) is present in an amountof from 0.001 mol-% to 20 mol-%, based on the monomer or monomermixture.

In case of monomer mixtures an average molecular weight is calculated.

Preferably the free radical initiator is present in an amount of from0.01 mol-% to 20 mol-%, more preferably from 0.1 mol-% to 10 mol-% andmost preferably from 0.2 mol-% to 5 mol-%, based on the monomer ormonomer mixture.

Preferably the molar ratio of free radical initiator to stable freenitroxyl radical is from 20:1 to 1:2, more preferably from 10:1 to 1:2.

The temperature for polymerization is preferably from 60° C. to 180° C.,more preferably from 80° C. to 140° C. and most preferably from 80° C.to 110° C.

The pressure during the reaction depends on the temperature applied andis preferably between 0.1 bar and 20 bar, more preferably between 1 and10 bar.

The reaction mixture may also contain a buffer to adjust and maintainthe pH value, preferably between 4.5 and 9. Phosphate or citric acidbuffers are preferred.

The process is particularly useful for the preparation of blockcopolymers.

Block copolymers are, for example, block copolymers of polystyrene andpolyacrylate (e.g., poly(styrene-co-acrylate) orpoly(styrene-co-acrylate-co-styrene). They are usefull as adhesives oras compatibilizers for polymer blends or as polymer toughening agents.Poly(methylmethacrylate-co-acrylate) diblock copolymers orpoly(methylacrylate-co-acrylate-co-methacrylate) triblock copolymers)are useful as dispersing agents for coating systeme, as coatingadditives (e.g. theological agents, compatibilizers, reactive diluents)or as resin component in coatings (e.g. high solid paints) Blockcopolymers of styrene, (meth)acrylates and/or acrylonitrile are usefulfor plastics, elastomers and adhesives.

Furthermore, block copolymers of this invention, wherein the blocksalternate between polar monomers and non-polar monomers, are useful inmany applications as amphiphilic surfactants or dispersants forpreparing highly uniform polymer blends.

Particularly, emulsion polymerization is especially suitable to build-uppolymer particles with specific morphology. For example, core/shellstructures can be achieved by consecutively changing monomers duringpolymerization. These special particles are useful for improving impactresistance of plastics. Oftenly, these core/shell structures are polymerblends of at least two types of polymers which are formed within thepolymer particle during emulsion polymerization. By applying controlledfree radical polymerization during consecutive monomer feed, blockcopolymers are formed which improve the compatibilizing effect of thedifferent polymers within the polymer particle. Furthermore, core/shellstructures can be synthesized by grafting a different monomer duringemulsion polymerization on polymer particles containing unsaturations,e.g. butadiene (co-)polymers. Applying controlled free radicalpolymerization within this grafting process, graft polymers with uniformgraft arm lengths and even new graft polymers are accessible.

Consequently the formation of block and graft polymers is a subject ofthe present invention.

The (co)polymers of the present invention may have a number averagemolecular weight from 1 000 to 400 000 g/mol, preferably from 2 000 to250 000 g/mol and, more preferably, from 2 000 to 200 000 g/mol. Thenumber average molecular weight may be determined by size exclusionchromatography (SEC), matrix assisted laser desorption/ionization massspectrometry (MALDI-MS) or, if the initiator carries a group which canbe easily distinguished from the monomer(s), by NMR spectroscopy orother conventional methods.

The polymers or copolymers of the present invention have preferably apolydispersity of from 1.1 to 2, more preferably of from 1.2 to 1.8.

The average particle diameter of the dispersed polymer particles ispreferably from 25 nm to 1000 nm, more preferably 200 nm to 700 nm.Particle size may for example be measured by a high speed centrifuge orby photon correlation spectroscopy.

The particle size distribution may be monomodal or bimodal.

The process of emulsion polymerization per se is known and for exampledescribed in WO 99/00426 or in WO00/50480. It may be carried out as abatch process or in a continuous or semi continuous process.

The initiator and/or regulator may for example be added at the beginningof the reaction, however it is also possible to add one or the other inportions or continuously at the beginning and during the reaction.

Suitable surfactants or surface active compounds which may be added areknown in the art. The amounts typically used range from 0.01% by weightto 10% by weight, based on the monomer or monomers.

Suitable surface active compounds are protective colloids such aspolyvinylalcohols, starch, cellulose derivatives or copolymerscontaining vinylpyrrolidone. Further examples are given in “Houben-Weyl,Methoden der Organischen Chemie, Band XIV/1, Makromolekulare Stoffe, G.Thieme Verlag Stuttgart 1961, 411-420”.

Typical surfactants useful in the present invention are of nonionic,cationic or anionic type.

Examples for anionic surfactants are alkali and ammonium salts ofC₁₂-C₁₈alkylsulfonic acid, dialkyl esters of succinic acid or sulfuricacid halfesters of ethoxylated alkanoles. These compounds are known forexample from U.S. Pat. No. 4,269,749 and largely items of commerce, suchas under the trade name Dowfax® 2A1 (Dow Chemical Company).

Nonionic surfactants are for example aliphatic or araliphatic compoundssuch as ethoxylated phenols (mon, di, tri) with an ethoxylation degreeof 3 to 50 and alkyl groups in the range from C₄-C₉, ethoxylated longchain alcohols or polyethyleneoxide/polypropyleneoxide block copolymers.

The emulsion polymerization may be carried out as seed free process oraccording to a seed-latex process which seed latex may also be preparedin situ. Such processes are known and for example described in EP-A-614922 or in EP-A-567 812.

The present invention also encompasses in the synthesis novel block,multi-block, star, gradient, random, hyperbranched and dendriticcopolymers, as well as graft copolymers.

The polymers prepared by the present invention are useful for followingapplications:

adhesives, detergents, dispersants, emulsifiers, surfactants, defoamers,adhesion promoters, corrosion inhibitors, viscosity improvers,lubricants, rheology modifiers, thickeners, crosslinkers, papertreatment, water treatment, electronic materials, paints, coatings,photography, ink materials, imaging materials, superabsorbants,cosmetics, hair products, preservatives, biocide materials or modifiersfor asphalt, leather, textiles, ceramics and wood.

Because the present polymerizaton is a “living” polymerization, it canbe started and stopped practically at will. Furthermore, the polymerproduct retains the functional alkoxyamine group allowing a continuationof the polymerization in a living matter. Thus, in one embodiment ofthis invention, once the first monomer is consumed in the initialpolymerizing step a second monomer can then be added to form a secondblock on the growing polymer chain in a second polymerization step.Therefore it is possible to carry out additional polymerizations withthe same or different monomer(s) to prepare multi-block copolymers.

Furthermore, since this is a radical polymerization, blocks can beprepared in essentially any order. One is not necessarily restricted topreparing block copolymers where the sequential polymerizing steps mustflow from the least stabilized polymer intermediate to the moststabilized polymer intermediate, such as is the case in ionicpolymerization. Thus it is possible to prepare a multi-block copolymerin which a polyacrylonitrile or a poly(meth)-acrylate block is preparedfirst, then a styrene or butadiene block is attached thereto, and so on.

The following examples illustrate the invention.

General

Polymers are characterized by gel-permeation-chromatography (GPC), witha Hewlett Packard HP 1090 LC, column PSS 1, length 60 cm, elution withtetrahydrofurane (THF), rate 1 ml/min, concentration 10 mg polymer in 1ml THF, Calibration with styrene. Polydispersity is calculated from Mn(g/mol) and Mw (in g/mol) as PD=Mw/Mn.

Log p is calculated using the following program:

LOGKOWNT program (Windows NT console application)

Syracuse Research Corporation

6225 Running Ridge Road

North Syracuse

N.Y. 13212

Nitroxyls

Nitroxyls are prepared according to GB 2335190 and GB 2342649.

Initiators

Initiators used are commercial products of Aldrich and WAKO Chemicals.

Emulsion Polymerization

Examples 1-10 are carried out using 40 g styrene, 320 g water and 1.8 gsodium dodecylsulfate. The mixture is degassed with argon.

For examples 1-10 the initiator is either 0.3322 g WAKO VA086(commercial azo-initiator) or 0.3115 g potassium peroxodisulfate (KPS),both dissolved in additional 20 g water and degassed with argon.

The nitroxyl radicals are added as indicated in Table 1 either dissolvedin additional 20 g water or in additional 20 g styrene degassed withargon.

Polymerization at 100° C.

Polymerization at 100° C. is carried out in a three neck flask withreflux condenser, dropping funnel with nitrogen balloon and stirrer.

The regulator solution and the styrene water mixture are filled into thethree neck flask under nitrogen atmosphere under stirring with 320rounds per minute. The mixture is heated to 100° C. in 45 minutes andthe initiator solution is dropwise added within 2 minutes. The reactionmixture is kept at 100° C. for 23 hours and stirred with 320 rounds perminute. After cooling down the reaction mixture and drying the residueunder vacuum the yield is determined gravimetrically. Polymercharacterization is carried out from a solution of the polymer intetrahydrofurane.

Polymerization at 120° C.

Polymerization at 120° C. is carried out in a double wall three neckflask with reflux condenser, pressuring and vacuum unit and stirrer.

Polymerization is carried out as described above with the followingdifferences: stirring speed: 600 rounds per minute; nitrogen pressure: 5bar, temperature: 120° C.; and reaction time 9 hours.

The polymerization runs are given in Table 1.

TABLE 1 Amount Tempera- Nitroxyl ture/Time No. InitiatorNitroxyl-Radical [g] log p [° C./h] B1 KPS

0.6859 2.6 100/23 dissolved in styrene B2 KPS

0.6226 3.0 100/23 dissolved in Styrene B3 KPS

0.9607 2.2 100/23 dissolved in water B4 VA086

0.9274 2.6 120/9 dissolved in styrene B5 VA086

0.6234 3.0 120/9 dissolved in styrene B6 VA086

0.5932 3.0 120/9 dissolved in styrene B7 VA086

0.5187 2.2 120/9 dissolved in water B8 VA086

0.2963 3.0 100/23 dissolved in styrene B9 KPS

0.3078 3.0 100/23 dissolved in styrene B10 VA086

0.2278 3.0 100/23 dissolved in styrene

The results are given in Table 2.

TABLE 2 Mn Mw Yield No. [g/mol] [g/mol] PD [1%] B1 8.800 9.700 1.1 48 B210.800 13.000 1.2 64 B3 23.200 27.300 1.2 80 B4 3.700 4.500 1.2 21 B57.500 9.100 1.2 32 B6 6.300 7.700 1.2 22 B7 19.000 25.000 1.3 57 B818.000 22.100 1.2 34 B9 15.000 17.700 1.2 62 B10 33.000 41.400 1.3 44

EXAMPLES B11 AND B12 Variation of Initiators

The emulsion polymerizations are performed as described in the generalprocedure but by varying the type and amount of initiators. Furthermore,the amount of nitroxyl compound No. 102 is varied. The examples aresummarized in Table 3.

TABLE 3 Amount Nitroxyl Amount of Initiator Compound No. 102 No. Type ofInitiator [g] [g] B11 WAKO V-50 0.3151 0.2965 B12 tert-BuOOH 0.11760.4141

All polymerizations are carried out at 100° C. for 23 h. The results arepresented in Table 4.

TABLE 4 Mn Mw Yield No. [g/mol] [g/mol] PD [%] B11 14200 16000 1.1 30B12 1.500 1.700 1.1 5

Comparative polymerization runs are given in Table 5 and 6.

TABLE 5 Amount Temperature/ Nitroxyl Time No. Initiator Nitroxyl-Radical[g] log p [° C./h] V1 VA086 — — — 100/23 V2 KPS — — —  85/23 V3 VA086

0.9620 7.9 120/9 dissolved in styrene V4 VA086

0.9594 7.9 100/23 dissolved in styrene V5 KPS

0.9658 7.9 100/23 dissolved in styrene

The results of the comparative examples are presented in Table 6.

TABLE 6 Mn Mw Yield No. [g/mol] [g/mol] PD [%] V1 253.000 943.000 3.7100 V2 95.000 397.000 4.2 100 V3 7.000 158.000 23 13 V4 383.0001,046.000 2.7 77 V5 49.000 538.000 11 85

From the comparative experiments it becomes apparent that PD exceeds 2significantly, indicating that essentially no control of thepolymerization exists.

EXAMPLE B13 Emulsion Polymerization of n-butylacrylate

Following formulation is emulsion polymerized at 100° C. for 23 h asdescribed in the general procedure:

60 g n-butylacrylate

344 g water

1.8 g sodium dodecylsulfate

0.2537 g potassium peroxodisulfate (KPS)

0.5099 g of compound No. 102

Yield: 6% GPC-results: Mn: 820 g/mol Mw: 930 g/mol PD: 1.1

EXAMPLE B14 Emulsion Co-Polymerization of n-butylacrylate and Zonyl®TA-M

Following formulation is emulsion polymerized at 120° C. for 9 h asdescribed in the general procedure:

40 g n-butylacrylate

20 g Zonyl TA-M (commercial available fluoro acrylate composition; CASRN 132324-93-7)

340 g water

1.8 g sodium dodecylsulfate

0.1080 g VA086

0.1587 g of compound No. 103

Yield: 34% GPC-results: Mn: 15.200 g/mol Mw: 17.500 g/mol PD: 1.2

EXAMPLE B15 Emulsion Co-Polymerization of Styrene and Acrylonitrile

Following formulation is emulsion polymerized at 100° C. for 23 h asdescribed in the general procedure:

60 g styrene

20 g acrylonitril

320 g water

1.8 g sodium dodecylsulfate

0.5169 g potassium peroxodisulfate (KPS)

0.6413 g of compound No. 102

Acrylonitril is added 30 min. after addition of the initiator.

Yield: 52% GPC-results: Mn: 17.300 g/mol Mw: 24.500 g/mol PD: 1.4

EXAMPLE B16 Re-Initiation of PS-Macroinitiator with Styrene

2.5 g of the product of example B5 are dissolved in 25 ml styrene. Thesolution is purged with Argon and heated for 24 h at 130° C. The productis precipitated in methanol and dried.

Yield: 90% GPC-results: Mn: 47.200 g/mol Mw: 60.000 g/mol PD: 1.3

EXAMPLE B17 Synthesis of Polystyrene-Block-n-Butylacrylate:

5 g of the product of example 85 are dissolved in 25 g n-butylacrylate.The solution is purged with Argon and heated for 24 h at 145° C. Theproduct is precipitated in methanol and dried.

Yield: 14% GPC-results: Mn: 13.000 g/mol Mw: 16.500 g/mol PD: 1.3

EXAMPLE B18 Re-Initiation of PS-Macroinitiator with Styrene

5 g of the product of example B9 are dissolved in 50 ml styrene. Thesolution is purged with Argon and heated for 24 h at 130° C. The productis precipitated in methanol and dried.

Yield: 77% GPC-results: Mn: 69.000 g/mol Mw: 99.400 g/mol PD: 1.4

EXAMPLE B19 Synthesis of Polystyrene-Block-n-butylacrylate

5 g of the product of example B9 are dissolved in 25 g n-butylacrylate.The solution is purged with Argon and heated for 24 h at 145° C. Theproduct is precipitated in methanol and dried.

Yield: 38% GPC-results: Mn: 24,500 g/mol Mw: 34,600 g/mol PD: 1, 4

EXAMPLE B20 Synthesis of Polystyrene-Block-n-butylacrylate in Emulsion(One Pot)

Following formulation is emulsion polymerized at 100° C. for 36 h asdescribed in the general procedure:

60 g styrene

340 g water

1.8 g sodium dodecylsulfate

0.3122 g potassium peroxodisulfate (KPS)

0.6211 g of compound No. 102

After 36 h, a sample is taken and the molecular weight distribution ischaracterized:

GPC-results: Mn: 17.900 g/mol Mw: 23.600 g/mol PD: 1, 3

After adding 60 g n-butylacrylate drop wise within 15 min, the emulsionpolymerization is continued for additional 60 hours at 100° C. Theproduct is worked-up according to the general procedure describedbefore.

Overall conversion: 63% GPC-results: Mn: 25.000 g/mol Mw: 32,400 g/molPD: 1, 3

The block copolymer is analyzed by ¹H-NMR (CDCl₃-solution), whichrevealed following co-monomer composition:

First block: 100 mol % styrene Second block:  69 mol % n-butylacrylate,31 mol % styrene.

What is claimed is:
 1. A process for preparing an oligomer, a cooligomer, a polymer or a copolymer (block or random) by free radical polymerization in aqueous dispersion of at least one ethylenically unsaturated monomer or oligomer, which comprises forming an aqueous dispersion having the monomer in the disperse phase and (co)polymerizing the monomer or monomers/oligomers at elevated temperature in the presence of a) at least one stable free nitroxyl radical which has a log p (octanol/water) of between −0.5 and 7.5 and which is selected from the group consisting of a compound of formula (A), (B), (C), (D), (E), (F), (G), (H) or (I)

wherein R is hydrogen, C₁-C18alkyl which is uninterrupted or interrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic carboxylic acid having 2 to 18 carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or an α,β-unsaturated carboxylic acid having 3 to 5 carbon atoms or of an aromatic carboxylic acid having 7 to 15 carbon atoms; R₁₀₁ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl; R₁₀₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl, C₂-C₈alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, or is glycidyl, a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z or —CONH—Z wherein Z is hydrogen, methyl or phenyl; G₆ is hydrogen and G₅ is hydrogen or C₁-C₄alkyl, and G₁ and G₃ are methyl and G₂ and G₄ are ethyl or propyl or G₁ and G₂ are methyl and G₃ and G₄ are ethyl or propyl; R₁, R₂, R₃ and R₄ independently of each other are C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl which are substituted by OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkyl which is interrupted by at least one O atom and/or NR₅ group, C₃-C₁₂cycloalkyl or C₆-C₁₀aryl or R₁ and R₂ and/or R₃ and R₄ together with the linking carbon atom form a C₃-C₁₂cycloalkyl radical; R₅, R₆ and R₇ independently are hydrogen, C₁-C₁₈alkyl or C₆-C₁₀aryl; R₈ is hydrogen, OH, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl; C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl which are substituted by one or more OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkyl which is interrupted by at least one O atom and/or NR₅ group, C₃-C₁₂cycloalkyl or C₆-C₁₀aryl, C₇-C₉phenylalkyl, C₅-C₁₀heteroaryl, —C(O)—C₁-C₁₈alkyl, —O—C₁-C₁₈alkyl or —COOC₁-C₁₈alkyl; and R₉, R₁₀, R₁₁ and R₁₂ are independently hydrogen, phenyl or C₁-C₁₈alkyl; and b) a free radical initiator; wherein the molar ratio of free radical initiator to stable free nitroxyl radical is from 20:1 to 1:2.
 2. A process according to claim 1, wherein in formula A, B and C R is hydrogen, C₁-C₁₈alkyl, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic, carboxylic acid; R₁₀₁ is C₁-C₁₂alkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl; R₁₀₂ is C₁-C₁₈alkyl, glycidyl, a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z, wherein Z is hydrogen, methyl or phenyl.
 3. A process according to claim 1, wherein in formula (D), (E), (F), (G), (H) and (I) at least two of R₁, R₂, R₃ and R₄ are ethyl, propyl or butyl and the remaining are methyl; or R₁ and R₂ or R₃ and R₄ together with the linking carbon atom form a C₅-C₆cycloalkyl radical and one of the remaining substituents is ethyl, propyl or butyl.
 4. A process according to claim 1, wherein the free radical initiator of component b) is a bis-azo compound, a peroxide or a hydroperoxide.
 5. A process according to claim 1, wherein the nitroxyl radical of component a) is present in an amount of from 0.001 mol-% to 20 mol-%, based on the monomer or monomer mixture.
 6. A process according to claim 1, wherein the free radical initiator is present in an amount of 0.01 mol-% to 20 mol-%, based on the monomer or monomer mixture.
 7. A process according to claim 1, wherein the temperature for polymerization is from 60° C. to 180° C.
 8. A process according to claim 1, wherein the pressure during the reaction is between 0.1 bar and 20 bar.
 9. A process according to claim 1, wherein the ethylenically unsaturated monomer is selected from the group consisting of styrene, substituted styrene, conjugated dienes, acrolein, vinyl acetate, vinylpyrrolidone, vinylimidazole, maleic anhydride, (alkyl)acrylic acidanhydrides, (alkyl)acrylic esters, (meth)acrylonitriles, (alkyl)acrylamides.
 10. A process according to claim 9, wherein the ethylenically unsaturated monomer is selected from the group consisting of styrene, acrylic acid ester, acrylamide, acrylnitrile, methacrylic acid ester, methacrylamide, methacrylnitrile.
 11. A process according to claim 1, wherein the polymer formed is a block copolymer or a graft copolymer. 